A Generalized Diffusion Tensor for Fully Anisotropic Diffusion of Energetic Particles in the Heliospheric Magnetic Field

The spatial diffusion of cosmic rays in turbulent magnetic fields can, in the most general case, be fully anisotropic, i.e. one has to distinguish three diffusion axes in a local, field-aligned frame. We reexamine the transformation for the diffusion tensor from this local to a global frame, in which the Parker transport equation for energetic particles is usually formulated and solved. Particularly, we generalize the transformation formulas to allow for an explicit choice of two principal local perpendicular diffusion axes. This generalization includes the 'traditional' diffusion tensor in the special case of isotropic perpendicular diffusion. For the local frame, we motivate the choice of the Frenet-Serret trihedron which is related to the intrinsic magnetic field geometry. We directly compare the old and the new tensor elements for two heliospheric magnetic field configurations, namely the hybrid Fisk and the Parker field. Subsequently, we examine the significance of the different formulations for the diffusion tensor in a standard 3D model for the modulation of galactic protons. For this we utilize a numerical code to evaluate a system of stochastic differential equations equivalent to the Parker transport equation and present the resulting modulated spectra. The computed differential fluxes based on the new tensor formulation deviate from those obtained with the 'traditional' one (only valid for isotropic perpendicular diffusion) by up to 60% for energies below a few hundred MeV depending on heliocentric distance.Comment: 8 pages, 6 figures, accepted in Ap

Status quo: Levels of Campylobacter spp. and hygiene indicators in German slaughterhouses for broiler and turkey

Poultry is a common reservoir for Campylobacter and a main source for human campylobacteriosis. With broiler being the predominant poultry for food production, most food safety related research is conducted for this species, for turkey, few studies are available. Although animals are typically colonized at the farm level, the slaughtering process is considered an important factor in re- and cross-contamination. We examined the development of Campylobacter, E. coli and total colony counts (TCC) after several processing steps in three broiler and one turkey slaughterhouses. Whole carcass rinsing and neck skin sampling was applied for broilers resulting in 486 samples in total, while 126 neck skin samples were collected for turkeys. A decrease in the loads of the different bacterial groups along the broiler slaughtering process was observed. Campylobacter mean counts dropped from 4.5 ± 1.7 log10 CFU/ml after killing to 1.6 ± 0.4 log10 CFU/ml after chilling. However, an increase in Campylobacter counts was evident after evisceration before the values again decreased by the final processing step. Although the Campylobacter prevalence in the turkey samples showed a similar development, the bacterial loads were much lower with 1.7 ± 0.3 log10 CFU/g after killing and 1.7 ± 0.4 log10 CFU/g after chilling compared to those of broilers. The loads of E. coli and total colony count of turkey were higher after killing, were reduced by scalding and remained stable until after chilling. This study highlights trends during the slaughtering process in reducing the levels of Campylobacter, E. coli, and total colony counts for broiler and turkey carcasses, from the initial step to after chilling. These results contribute to our understanding of microbial dynamics during meat processing

Shot noise of a quantum dot with non-Fermi liquid correlations

The shot noise of a one-dimensional wire interrupted by two barriers shows interesting features related to the interplay between Coulomb blockade effects, Luttinger correlations and discrete excitations. At small bias the Fano factor reaches the lowest attainable value, 1/2, irrespective of the ratio of the two junction resistances. At larger voltages this asymmetry is power-law renormalized by the interaction strength. We discuss how the measurement of current and these features of the noise allow to extract the Luttinger liquid parameter.Comment: 4 pages, 3 figures,to be published in Phys. Rev. B. For high resolution image of Fig.1 see http://server1.fisica.unige.it/~braggio/doc.ht

Luminescence from highly excited nanorings: Luttinger liquid description

We study theoretically the luminescence from quantum dots of a ring geometry. For high excitation intensities, photoexcited electrons and holes form Fermi seas. Close to the emission threshold, the single-particle spectral lines aquire weak many-body satellites. However, away from the threshold, the discrete luminescence spectrum is completely dominated by many-body transitions. We employ the Luttinger liquid approach to exactly calculate the intensities of all many-body spectral lines. We find that the transition from single-particle to many-body structure of the emission spectrum is governed by a single parameter and that the distribution of peaks away from the threshold is universal.Comment: 10 pages including 2 figure

The Origin, Early Evolution and Predictability of Solar Eruptions

Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt

Electrophoresis Poly(Dimethylsiloxane)/Glass Chips with Integrated Active Cooling for Quantification of Amino Acids

International audienc

High Spatial Resolution and High Contrast Visualization of Brain Arteries and Veins: Impact of Blood Pool Contrast Agent and Water-Selective Excitation Imaging at 3T

Purpose To investigate a blood pool contrast agent and water-selective excitation imaging at 3T for high spatial and high contrast imaging of brain vessels including the veins Methods and Results 48 clinical patients (47 +/- 18years old) were included Based on clinical findings twenty-four patients received a single dose of standard extracellular Gadoterate-meglumine (Dotareme (R)) and 24 received the blood pool contrast agent Gadofosveset (Vasovist (R)) After finishing routine MR protocols, all patients were investigated with two high spatial resolution (0 15 mm(3) voxel size) gradient echo sequences in random order in the equilibrium phase (steadystate) as approved by the review board A standard RF-spoiled gradient-echo sequence (HR-SS TR/TE 5 1/2 3 msec, FA 30 degrees) and a fat-suppressed gradient-echo sequence with water-selective excitation (HR-FS 1331 binominal-pulse, TRITE 8 8/3 8 msec FA 30 degrees) The images were subjectively assessed (image quality with vessel contrast artifacts depiction of lesions) by two investigators and contrast-to-noise ratios (CNR) were compared using the Student's t-test The image quality and CNR in the HR-FS were significantly superior compared to the HR-SS for both contrast agents (p < 0 05) The CNR was also improved when using the blood pool agent but only to a minor extent while the subjective image quality was similar for both contrast agents Conclusion The utilized sequence with water-selective excitation improved image quality and CNR properties in high spatial resolution imaging of brain arteries and veins The used blood pool contrast agent improved the CNR only to a minor extent over the extracellular contrast agen